Uncertain results in study of convalescent serum for COVID-19

An undated handout photo shows Dr. Benjamin Planer while donating plasma after tests showed he was no longer positive for the coronavirus. The New Jersey doctor’s blood was found to have high levels of virus antibodies. Researchers plan to use it to treat other patients. (Handout via The New York Times)

A small study of patients who were severely ill from the coronavirus hints that treatment with antibodies from recovered patients may help recovery and survival, scientists reported Friday.

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The study, although far from conclusive, is said to be the largest of subjects recovering from COVID-19, the illness caused by the coronavirus. Thirty-nine hospitalised patients were given intravenous infusions of antibodies from patients who had recovered from the condition.

The course of illness in patients who received the convalescent plasma was compared to that of similar patients identified through electronic health records who did not get the treatment. This is a weak form of comparison, prone to error. And researchers are wary of studies that take place at a single institution because the results often are not applicable to patients elsewhere.

Researchers at Mount Sinai School of Medicine in New York reported that 18% of those who got the plasma of convalescent serum got sicker, compared with 24.3% of patients identified through medical records.

The death rates were 12.8% among those who got the antibodies, compared with 24.4% among the patients who did not get this treatment.

The researchers provided percentages but not actual numbers of patients. And studies like these are fraught with difficulties. The only way to know for sure if the treatment works is to randomly assign patients to receive antibodies or a placebo.

And it can be impossible to find many patients who agree to have their treatment randomised to an unknown treatment, refusing plasma treatment, noted Dr. Arturo Casadevall of the Johns Hopkins School of Medicine in Baltimore.

The Food and Drug Administration has approved the use of convalescent serum in very sick patients. Few hospitalised patients may want to forgo a treatment that appears to be safe and might be effective.

“That train has left the station,” Casadevall said.

Another idea, favoured by researchers elsewhere, is a randomised trial to see if antibodies from recovered patients can prevent infections in health care workers who are at high risk of being infected.

The goal is to have a multicentre trial, to avoid the distortions that can arise when all the data come from one medical centre. Researchers not associated with the study will assess efficacy.